The Immunoassay Core Facility provides assay services that are tailored to the needs of the members of the Cancer Center. The facility has provided services to a number of the Programs of the Center: Hormone Action and Signal Transduction in Cancer, Breast Cancer, Prostate Cancer, and Cancer Prevention. New assays have been developed to meet special needs. For epidemiologic studies highly sensitive direct assays for salivary estradiol and progesterone have been developed and validated. In addition, methods for assay of growth factors EGF, TGF-alpha, and TGF-beta in breast fluid have been developed. Recently, validation of methods for assay of estradiol and other steroid hormones in breast fluid have been completed. Having the capacity to develop procedures for new projects within specific contexts permits the facility to provide assay services that are not available commerically. Even with the use of commercial kits, combining the work of many projects in one laboratory dedicated to immunoassay provides better quality control and prices that are lower because of economy of scale than similar assays performed in individual laboratories. Techniques available include radioimmunoassay, enzyme immunoassay (ELISA), and time-resolved immunofluorescence assay. Binding properties of ligands may also be quantified. Having the experience in production of antiserum for a number of hormones and having monoclonal antibodies available from the Monoclonal Antibody Core Facility, this facility is able to prepare immunoassays for new biologically significant compounds that are needed by researchers at Northwestern. The facility has experience in sample preparation and sample purification procedures that are often necessary for accurate and valid measurements of hormones and other factors. The facility also works closely with investigators to meet specific goals of their research by providing results to them on a daily or weekly basis so that they can follow the progress of the research. In some cases this provides information necessary to make decisions about continuing, making adjustments, or terminating protocols. Methods applicable to both clinical and basic research are available.